Iris diaphragm for photographic or cinematographic objectives



H. MAHN 3,005,395

IRIS DIAPHRAGM FOR 'PHOTOGRAPHIC OR CINEMATOGRAPHIC OBJECTIVES Oct. 24, 1961 Filed July 10, 1959 Inventor? flererf MAHN United States Patent i 3,005,395 IRIS DIAPHRAGM FOR PHOTOGRAPHIC OR ClNEMATOGRAPI-IIC OBJECTIVES Herbert Mahn, Kreuznach, Rhineland, Germany, assignor to Jos. Schneider & Co., Optische Werke, Kreuznach, Rhineland, Germany, a corporation of Germany Filed July 10, 1959, Ser. No. 826,362 Claims priority, application Germany Aug. 9, 1958 4 Claims. (Cl. 95-64) -My present invention relates to iris diaphragms as used in photographic or cinematographic objectives to control the efiective aperture of a lens system.

Conventional iris diaphragms generally comprise a plurality of overlapping, arcuate leaves each with a pair of more or less Widely separated pivot pins, one pin of each leaf being rotatably journaled in a first ring which is concentric with and rotatable relatively to a second ring having an array of grooves to accommodate the remaining pins. As the two rings are rotated with respect to each other, the iris leaves are swung about their fulcra in the first ring through the camming action of the grooves of the second ring to define a central aperture of variable diameter, the range of adjustment ideally extending from zero or near zero to a diameter close to or equaling the inner diameter of the concentric rings.

A disadvantage of this type of iris diaphragm is that the movement of the leaves is determined by the shape of the guide grooves which in turn is subject to definite limitations, owing to the contradictory requirements for a pitch angle whichis high enough to avoid the intersection of grooves yet low enough to facilitate the camming displacement of the leaves. This situation imposes restrictions on the number of leaves that can be accommodated in an iris diaphragm of given external dimensions; it also militates against the establishment of a linear or near-linear relationship between the diaphragm aperture and the displacement angle of the movable setting ring as read on the usual diaphragm scale.

The general object of my present invention is to provide an improved iris diaphragm affording greater freedom of design.

Anotherobject of this invention is to provide a simplified mechanism for controlling the adjustment of a set of iris leaves.

'A more particular object of the present invention is to .provide an iris' diaphragm whose manual resetting is not encumbered by the presence of a ring or other guide member having a multiplicity of camming surfaces.

The invention realizes the above objects through the provision of an array of iris leaves which are pivotally mounted in a single ring and are provided with abutments whereby each leaf bears upon its neighbor to impart to it a displacement similar to its own displacement under the action of a control element or of an adjoining leaf. Preferably, in accordance with a more specific feature of this invention, the leaves (or at least those to which movement is not communicated directly by an external control element) are provided with studs hearing upon the curved inner, aperture-defining surfaces of the adjoining leaves for mutual entrainment in a generally radial direction along orbital paths about their respective fulcra.

It is possible cyclically to interconnect all the leaves in the manner described to form a closed system in which either an inward or an outward displacement of any leaf will positively entrain all the other leaves in the same sense. The invention may, however, also be embodied in a system in which the leaves bear upon one another in an open chain, with the first member of the chain subject to displacement by a control element and the last member of the chain subject to the action of a restoring Patented Oct. 24, 1961 ice force. In this latter case it is also possible to divide the multiplicity of iris leaves into a plurality of such chains, preferably with the externally driven member of each chain operatively coupled to the same control element. The restoring force, pursuantto a further feature of this invention, is advantageously derived from an open annular spring also serving as a means for keeping the leaves anchored to their mounting ring.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 shows in axial section an irisdiaphgram embodying the invention;

FIG. 2 is a view similar to FIG. 1 showing a modified diaphragm;

FIG. 2a is a fragmentary view of the diaphragm of FIG. 2 taken in radial section; and

FIG. 3 shows a further modification in a view similar to those of FIGS. 1 and 2.

The iris diaphragm shown in FIG. 1 comprises a'cylindrical housing a with an annular shoulder a" on which a series of iris leaves 11 are swingably mounted by means of angularly equidistant pivot pins c. The curved inner surfaces d of the leaves b define an adjustable iris aperture as is well known per se. Each of these leaves is provided with a stud e which rests against the surface d of an adjoining leaf whereby all of these leaves are interconnected for movement in unison when any one of them is caused by external means to swing about its pivot c. In order to bring about such movement, one of the leaves, designated b is articulated at g to a control lever 1 which passes through a slot a in housing a and can be displaced in the direction of arrow I with the aidof a suitably'graduated, manually operable diaphragmsetting member not shown.

. The system of FIGS. 2 and 2a is similar to that of FIG. 1, except that one of the iris leaves, designated b lacks a stud e and is instead provided with a spur b this spur passing through the slot a in housing a and through a similar slot i in a surrounding setting ring h which is concentrically rotatable about the housing as indicated by arrow II. An open annular spring, 1', of

preceding the externally controlled leaf b i. It will thus be seen that the leaves b of FIG.' 2 do not constitute fa closed ring, as in FIG. 1, but represents a chain whose first member is the leaf h and whose last member is the leaf I1 If setting ring h in FIG. 2 is rotated counterclockwise relatively to housing a, the upper edge i' of its-slot i earns the spur k of leaf b inwardly to impart a diaphragm-closing inward movement to all the leaves of the system, thus movement occurring against the restraining action of restoring spring 1'; if ring h is then rotated clockwise, spring j reopens the diaphragm by forcing the stud m radially outwardly, the resulting outward swing movement of leaf b being imparted in counterclockwise succession to all the iris leaves, up to and including leaf b to the extent permitted by the receding edge i of slot i.

In FIG. 3 the iris leaves b include two externally driven, diametrically opposite leaves b b32 whose spurs b b32 pass through slots in housing a and are operatively engaged by respective internal cams n n, of a setting ring h, this ring being rotatable about housing a as indicated by arrow III. The extremities of restoring spring 1' bear upon pins m m of two other iris leaves which respectively precede the leaves b I732 and are the end members of two three-leaf chains respectively controlled by the cams n and n Spring j' acts as a snap ringfto hold the leaves in place, as described for spring 1' in connectionwith the ..pre ceding embodiment. r

Since only the shape of the cams n n determines the law of motion of the leaves b in FIG. 3, it is possibleto vary this :law bythe. use-ofmodified'cams. Thus, Lhave. indicatedin dot-dash lines the possibility. of providing? additional cam surfaces n n .of different slope or configuration, for adjusting the diaphragm opening in accordance with .a separate,..scale .The invention, ac.- cordingly,.,enables the utilization of. two or moreldiaphragm ,scalesfor manually or automatically resetting a single iris aperture ,by different increments. Itlwill be apparentthat; thesys'tems of FIGS. 1 and 2 lend themselves infanalogous' manner to selective operation by a plurality ofcontrol elements, depending upon the "sensitivity of the film, the presence of a filter or similar expos'urermodifying factors.

My invention is, of course, not limited to the specific embodimentsldescribedand illustrated but may be realized in various modifications'without departing from the spirit. and scope of the appended claims.

I claim:

,1. An iris diaphragm for optical objectives, comprising an annular support, aiplurality of iris leaves pivotally mounted on. said support at angularly spaced locations and;in mutually. overlapping relationship, said leaves defining a variable iris aperture, control means operatively engaging at leastone of said leaves for swinging it about its pivot, adjacent ones of said leaves being'provided with co-operating formations for displacing all of said leaves in the-same sense .upon a displacement of said oneof saidcleavesbyusaid control means, and restoring spring means, anchored to at least one other of said leaves in opposition to. the displacement of said leaves by said control means saidc formations interconnecting said necting said, leaves in a plurality of chains each starting with oneof said engaged leaves, said springmea'ns being anchored -to the last leafsof eachchain', said'control means comprising-asetting member provided with a plurality of synchronized cams respectively'bearingupon said-,engagedleaves'. s i

,2. An iris diaphragmfor optical objectives, comprising a cylindrical housin'g'with an annular shoulder, a

. 4 I plurality of iris leaves pivotally mounted on said shoulder at.angularly. equidistant locations and in mutually overlapping relationship, said leaves being provided with curved internal surfaces defining a variable iris aperture, control means operatively engaging at least one of said leaves for swinging it about its pivot, and studs on at least the remainingleaves each in contact with the ap'erture-defining surface of an immediately preceding leaf whereby an aperture-changing displacement of said one of said leaves by said control means is communicated to each of said remaining leaves, said control meanscomprisinga ring concentrically surrounding said housing with freedom of rotation relative thereto, said one of said leaves being provided with an extension projecting beyond said-housing, said ring being provided with a camming surface bearing upon said extension.

3. A diaphragm according to claim 2 wherein said housing is provided with an internal annular groove separated from said shoulder bysaid leaves, further comprising a resilient snaprin'g partly received in said groove and overlying said leaves, said ring bearing upon a leaf immediately preceding said one of said leaves in a sense opposing the aperture-changing displacement of the leaves by said control means.

.4. An iris diaphragm for optical objectives, comprising an annular support, a plurality of iris leaves pivotally mounted on said support at angularly spaced locations and in mutually overlapping relationship, said leavesde fining a variable iris aperture, control means operatively engaging at least one of said leaves for swinging it about its pivot, adjacent ones of .said leaves being provided with co-operating. formations for displacing all of said leaves in thesame sense upon a displacement of said one of said leaves by said control means, and restoring spring means beingadapted to displace all of said leaves in a given sensethrojugh the intermediary of said one of said leaves, said control means including a ring concentrically rotatable about said support, said one of said leaves being provided with an extension in camming engagement with said ring.

References Cited in the file of this patent UNITED STATES PATENTS Bausch May'15, 1888 Brueck Sept. 6, 1938 

